Overweight and Obesity Are Associated with Somatization Symptoms in a Health Examination Population

Background According to World Health Organization data, the global obesity rate has nearly tripled since 1975, becoming a major public health concern. Obesity is closely associated not only with cardiovascular diseases and diabetes but also with mental health disorders such as depression and anxiety, though the underlying mechanisms remain incompletely understood. This study aimed to retrospectively investigate the relationship between obesity and mental health, as well as potential physiological mechanisms, within a health examination population. Methods We conducted a retrospective cross-sectional analysis using data from individuals who underwent routine health check-ups at a tertiary hospital in Beijing. Archived questionnaire data, including the Symptom Checklist-90 (SCL-90) and the Stress Self-Assessment Questionnaire-53 (SSQ-53), were used to assess mental health status. Archived hematological biomarkers were analyzed to evaluate physiological status. Statistical analyses included the Benjamini-Hochberg procedure for False Discovery Rate (FDR) correction, multiple linear regression, and binary logistic regression to identify factors associated with psychological symptoms. Results The analysis included 10,751 participants (5,520 normal weight, 3,797 overweight, 1,434 obese). The somatization subscale score increased significantly with BMI. The obesity group had a significantly higher positive rate for somatization (factor score ≥ 2) compared to the other groups (P for trend = 0.026). Interestingly, the obese group reported significantly lower levels of emotional stress (FDR-adjusted P = 0.002) than the normal-weight group. Multivariable analysis confirmed that higher BMI, female gender, older age, and specific biochemical markers reflecting inflammation and metabolic dysregulation (e.g., elevated white blood cell count, decreased absolute lymphocyte count, all P < 0.05) were independently associated with more severe somatization symptoms. Conclusion In this retrospective health examination cohort, higher BMI was independently associated with increased somatization symptoms, with the association partly explained by related inflammatory and metabolic disturbances. Contrary to the common assumption of uniform psychological distress, the obese subgroup reported lower perceived emotional stress. This pattern hints at a complex and non-linear relationship between obesity and mental health. Further longitudinal research is needed to clarify the underlying causal pathways.